1. Field of the Invention
This invention relates generally to foundations for movable dwellings, such as mobile homes and commercial coaches, and more particularly, to an improved pier for supporting a movable dwelling that substantially resists environmental forces, such as seismic and wind forces.
2. Description of Related Art
Foundation piers are well known in the art. Piers are typically used to support beams, girders, floor joists, and the like. Piers are often used in the foundation systems of movable dwellings, such as mobile homes and commercial coaches for example. Since these dwellings are movable, foundation systems incorporating piers are a preferable system for supporting the dwelling, as the foundation system can be disassembled if it is desired to move the dwelling.
Movable dwellings typically comprise a prefabricated modular unit, with the length thereof substantially greater than the width, to provide ease of transporting the unit for example. The unit is typically fabricated with a plurality of spatially positioned, elongated support girders or beams that extend along the longitudinal axis of the unit. The support beams often have an "I" configuration. A plurality of spatially positioned floor joists are supported by the beams and extend across the width of the unit. Some movable dwellings may incorporate a perimeter chassis that has a beam having a "C" configuration.
Piers are used to support the beams and may be positioned beneath a beam, at an intersection of the beam and a joist. Units configured with C-beams may have piers spatially positioned along the beam at predetermined intervals to support the unit. The distance between the piers is governed by such factors as the dimensions of the unit and applicable building codes at the installation location of the unit, for example.
FIG. 1 of the drawings shows a schematic representation of a prior art pier 10. The prior art pier 10 shown comprises a base plate 12 for supporting the pier on the ground 13 and pair of opposing supports 14 affixed to the base 12. The supports 14 may comprise opposing portions of angle iron, for example, that extend perpendicular to each other. Extensions 16 are coupled to the supports 14 using bolt-nut combinations 18. A plurality of holes 20 may be disposed through the longitudinal axis of both the supports 14 and extensions 16.
The piers 10 are installed by adjusting the extensions 16 until a top portion 22 of the extensions 16 abuts a desired beam (not shown). The bolts 18 are then disposed through the holes 20, then nuts (not shown) then threaded onto the bolts 18 to secure the extensions 16 to the supports 14. The plurality holes 20 enable the extensions 16 to be secured to the supports 14 at different locations for adjusting the height of the pier 10.
The piers 10 may include means for coupling the extensions 16 to the beam. Such coupling means (not shown) may comprise a platform affixed to the top edge 22 of the extensions 16. The platform may have an upwardly extending threaded shaft at each corner thereof. A plate is held is a desired horizontal position by the threaded shafts using well known methods. The plate is adjusted upwardly until it abuts the desired beam. A pair of brackets that are coupled to the shafts, are then placed over the bottom portion of the desired beam. The brackets are then tightened onto the bottom portion of the beam. A disadvantage of the discussed coupling means, is that is was somewhat unstable due to the length of the shafts. Lateral forces applied to either the beam or the pier 10 could cause the coupling means to fail.
A further disadvantage of the discussed prior art pier, is that while the extensions 16 reside tightly against the supports 14, a substantial amount of force on the extensions 16 is transferred to the bolts 18, instead of the supports 14. Seismic activity and wind forces can substantially increase the amount of force applied to the pier 10, causing the bolts 18 to fail. Particularly, force applied to the bolts 18 from the extensions 16 may shear the bolts 18, causing the extensions 16 to suddenly drop. Thus, the pier 10 no longer supports the beam, which could result in damage to the unit and to the pier 10.
There therefore exists a need for a pier that resists environmental forces applied thereto due to seismic activity, wind, and the like, to prevent the pier from failing.